1. Field of the Invention
The invention relates to a ski boot comprising a rigid shell and at least one foot retention system positioned within the shell.
2. Description of Prior Art
Various embodiments of boots comprising a foot retention system have previously been developed. In particular, ski boots are known which are provided with a rigid plate positioned between the shell and an interior shoe. The plate is pressed vertically against the shoe by screws implanted in the upper portion of the shell base so as to retain the foot as is described in U.S. Pat. No. 3,883,964.
Likewise, ski boots are known whose foot retention system is of the type claimed in French Pat. No. 2,343,437, filed by Applicant, the disclosure of which is hereby incorporated by reference, which incorporates straps surrounding the foot and attached to the shell at each side thereof.
Furthermore, a ski boot is known whose foot retention is assured by a strap positioned perpendicularly to the axis of the boot which exerts a vertical force on the foot when it is place in tension by a strap buckle apparatus as is described in German Patent DE No. 18 16 811.
Finally, other foot retention systems are known for retaining the foot within the shell which are more particularly adapted to ski boots of the type which open in front. In these systems one utilizes the deformation properties of the walls to maintain the foot within the shell.
For the different types of boots described, the foot retention systems which are provided therein suffer from a certain number of disadvantages.
Particularly, for boots of the type which open to the rear such as are illustrated in U.S. Pat. No. 3,883,964 and German Patent DE No. 18 16 811, there is a relatively localized retention of the foot at the upper portion of the foot which is then vertically crushed without having any lateral retention, while in French Pat. No. 2 343 437, the retention of the foot in the boot is obtained by its maintenance on the inner sole by means of a set of straps whose assembly complexity increases the cost of such a boot.
With respect to boots of the type which open to the front, it appears that the deformation of the walls of the shell by strap systems attached to the interior of the shell and extending to the exterior thereof so that they can be tightened by means of a strap buckle, is not sufficient to provide the tightening and the necessary maintenance of the foot.